#include<stdio.h>
#include<assert.h>

size_t my_strlen(char* str)
{
	assert(str);
	char* ret = str;
	while (*str)
	{
		str++;
	}

	return str - ret;
}
int main()
{
	char* str = "abcdef";
	size_t len = my_strlen(str);
	printf("%zd\n", len);
	return 0;
}